SCIENTISTS are already in mourning as the Cassini spacecraft, which was launched on October 15, 1997, will expire in the clouds of Saturn on September 15, 2017, twenty years and a month later.
Although the Pioneer and Voyager missions took just three years to get as far as Saturn (approximately 1.2 billion kilometres at its closest point), Cassini took seven; because of it weighing in at six-tonnes it could not accelerate as quickly, and had to thus take a very circuitous route to the ringed gas giant.
Remember, everything is moving around the sun, so you cannot simply aim at a planet and fire because your target won’t be in the same place as when you sent it. In fact, the Earth takes a smidgen over a year to orbit the sun (365.25 days hence, every four years a leap year), but Saturn takes almost 29 and a half years for a complete orbit. Imagine how accurately you have to calculate both planets’ orbits to precisely reach Saturn from Earth. Also take into account that when we look at Saturn, the light has taken just over an hour to reach us, so we are not looking at where the planet is, but where it was an hour before.
Cassini has made a number of amazing discoveries since it reached Saturn in 2004 and has been in operation a full eight years longer than was intended. It has visited Saturn’s moon Titan and discovered the only other planet in the solar system (that we currently know of) that has a thick prominently nitrogen atmosphere like Earth, as well as liquid flowing on its surface. However, the liquid on Titan is methane, ethane and other hydrocarbons, not water. But this does not necessarily dismiss the chances that life is present on the moon. Titan is considerably larger than our own moon, and Cassini has photographed rivers, mountain ranges and dunes similar to Earth geological features.
When Cassini visited another moon, Enceladus which is much smaller than our moon, it detected salt water plumes emanating through the solid ice that forms the moon’s surface.
The Cassini mission has revealed many more secrets of our solar system and broadened our knowledge considerably. Now, however, the spacecraft has run out of fuel, so its final mission is to plunge into Saturn’s atmosphere and probably be crushed or burn up on entry. Either way, on September 15 we shall say our final goodbyes, and that is why space scientists are sad.